Prime Lenses: 50mm vs. 35

Back in December, I bought a new lens for my camera. I have a Sony NEX-3, which is pretty much a DSLR, but is about half the size and weight of a normal DSLR camera. One main draw of having a DSLR or similar camera over a point-and-shoot is that you can change the lenses. Read on for some technical insight as to why you would buy a different lens, and what the difference is. If you feel well-informed already, skip down to the fifth paragraph to learn whether you should buy the 50mm or 35mm lens if you are looking for a prime portrait lens.

Most people buy their first manual camera with a kit lens, which is normally a zoom lens with a focal length of something like 18-55m (mid-range) or 18-135mm (telephoto).  These lenses are great because they are very versatile, and give you a similar zoom range to what you are used to having on a point-and-shoot camera. You can shoot a wide angle of view, like a building with a yard in front of it, or a portrait of someone from the shoulders-up, or you can get a close-up of something that's kind of far away. The problem with these lenses is that because they cover such a wide range of focal lengths (aka distances you can shoot), they aren't super great at shooting at any one distance. Basically, you're sacrificing quality for convenience. (You can upgrade to better quality zoom lenses, but they are much more expensive than the kit lens.)

One obvious thing that you are sacrificing is aperture. Aperture is the setting that affects both how much light you can let in when taking a picture as well as depth of field, which is basically how much of your subject is in focus. With a wider aperture, you can 1. take pictures in lower light (because you can let more light in. In the human eye, this is measured by our pupils. Go in a dark room and look in the mirror - your pupils get really large! They are widening to let in more light.), and 2. make less of your picture in focus, making the background blurrier (this is how the human eye focuses. Try holding a pen in front of your face - notice how when you're looking at it, everything else goes out of focus. When you switch to looking at your surroundings, the pen goes out of focus.) Aperture is actually measured as a fraction, so a wider aperture is actually noted as a lower number. The widest aperture I'm aware of in existence is 1.2, whereas on the high end you could have an aperture of 22 or 32.

An example of being able to take pictures in not-very-bright situations. You can tell how dark this room was, yet you can clearly see each band member. This was taken with the aperture at f/1.8 and no flash was used.

This photo and the next are an example of the pen in front of your face illustration. This first picture is focused on the pen -you can barely tell what's in the background!

And now the focus switched to the moss. You can easily see the moss, but hardly notice the Christmas lights.

Eventually people wanting to grow in their photography feel limited by only having the kit lens. They want to be able to achieve creamy, blurry backgrounds that make the subject of their photos stand out more, like real life, and thus look more professional. The solution is buying a prime lens. A prime lens is just one that has a fixed focal length (like 16mm, 50mm, 85mm, etc.). These lens don't zoom, but they excel at the focal length they do offer. They have a wider aperture than a kit lens can give. For example, my kit lens has an aperture that ranges from f/3.5-5. Those numbers represent the widest aperture I can get when I am at different focal lengths. For example, I can shoot at f/3.5 when I'm at the closest focal length (18mm), but when I zoom in, to say 55mm, the widest aperture I can get is  f/5. With a prime lens, like my 16mm, I can only shoot wide angles, but the aperture opens as wide as f/2.8. With prime lenses, not only do you get blurrier backgrounds, but since the lens is higher quality, you normally achieve a crisper focus as well. Why are prime lenses higher quality? Because they are specializing in one thing. A zoom lens has to cover a wide variety of focal distances, so it's harder to get as good quality in each focal length for the price you're paying.

That was all introductory, so now for the point of this article: which prime lens should you buy to get that great crisp focus and blurry background? There are actually a lot of options out there depending on what you want to take pictures of. A lot of people are looking for a portrait lens, which gives you a little bit of zoom so that you can take great, crisp picture of people without having to stand really close to them. Lately, I have seen a lot of people choose to buy a 50mm lens to suit this purpose. I, on the other hand, bought a 35mm lens, which is what I would recommend to others who are looking to buy a prime portrait lens. Why?

I am not really sure the reason for people buying a 50mm portrait lens, but I think it may be because they have heard professional photographers rave about their 50mm. I follow several wedding photographers' blogs and for most of them, their 50mm is their favorite for portraits and all-around shooting. So then if you have a DSLR, why shouldn't you also buy a 50mm? The reason is that the photographers you follow are using professional cameras that have a full-frame sensor, while you probably have an amateur DSLR that has a cropped sensor. What the heck does that mean?

This might sound complicated, but it is actually simple - the sensor on your camera is cropped. If you draw a circle, and then draw a square inside of that circle, you come out with four ovals of space that are a part of the circle, but not a part of the square. Think of a full-frame sensor as being that circle - if you take a picture, you capture everything within that circle. Now compare the cropped sensor to the square - if you try to take a picture of everything within that circle, you come out short. You don't have the ability to take a picture of the whole circle, because your sensor, the square, is too small.

This may sound discouraging, but it's completely fine! That's the way your camera was made. However, it does affect the lenses you choose. Remember how we said that focal length was the distance you can shoot? That was fairly true, but also kind of misleading. Focal length is actually just a literal measure of how long your lens is. So an 18mm lens is 18mm long. Thus, focal length. Now, for someone with a full-frame sensor camera, the focal length WILL also be the measure of the distance they can shoot, which we will call the angle of view. So where's the discrepancy? For people with cropped sensor cameras, the angle of view is different from the focal length. This goes back to the circle/square dilemma. Even though you might possess a 50mm lens (the circle), when you take a picture you will only capture the information within the square, which in this case, turns out to be the same distance you would get if you used an 75mm lens on a camera with a full-frame sensor. This is because if you were using the circle, you would have to move closer or zoom in more to capture only the amount of information contained within the square. Does that make sense?

So, again, why would you choose the 35mm lens? If you want to buy that all-around versatile lens that almost every photographer has fallen in love with, if you have a cropped sensor camera (and you probably do, unless you spent thousands of dollars on your camera) you should buy a 35mm lens, because its angle of view equivalent IS about 50mm. On the other hand, if you buy a 50mm, you may be disappointed when you learn that to take portrait of people, you have to stand kind of far away from them to get their whole or part of their body instead of just their face. Now that may be what you're looking for, but just be warned that it is a fairly zoomy lens. A test you can do to see what focal length lens to get is to just zoom in your kit lens to the distances you're trying to choose between. When I did that, I discovered that I couldn't get very much in the frame when I had it set to 50mm, but when I put it on 35, I loved the amount of subject I could get in the picture. And yes, now that I have my 35, I feel as in love with it as most photographers do about their 50 - it is almost always my lens of choice!

For example, at Adam & Liz's wedding, I was only sitting a few rows back, but I was still able to capture the whole window in this picture by using my 35mm lens.

I hope that was helpful! Let me know if you have any questions. :)